Dynamo-electric machine.



s. RuBERGMAN 1111111110 ELECTRIC MACHINE.

APPLICATION FILED OCT. 13, 1915.

1,257,177. Patented Feb.19,1918.

Fig. 1 1

His Attorney.

Q UNITED STATES PATENT OFFICE.

SVEN R. BERGMAN, OF NAHANT, MASSACHUSETTS, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

nYNAMo-ELEcTmc MACH-HIE.

Specification of Letterslatent. t t 1 191 A ncauoa filed October 1a, 1915. serial No. 55,632.

Tool?- whom it may concern:

.Be it'known that I, Sven R. BERGMAN, asubject of the King of Sweden, residing at Nahant, in the county of Essex, State of Massachusetts, have inventcdcertain new and useful Improvements in D namo-lfilectr ic Machines, of which the 0 lowing is a specification.

My invention relates to dynamo-electric machines and particularly to direct current dynamorlectric machines. The object of.

my imeution is to provides, novel and improved direct current dynamo-electric machine. i.

-In its complete form my invention relates especially to-direct current dynamo ele'ctric machines adapted-for operation as motors and as generatorsof practically constant direct current eleetromotive force when operatim, zit-variable speed. Such machines are extensively usedin electric starting and lighting outlits on motor vehicles.' In such outfits 'tbe' dynamo-electrie machine is associatcd with an internal combustion engine yand a storage battery, and operates as a moquired, and it is usually found desirable to tor supplied with electric energy from the battery for startingthe engine and as a generator for charging the battery. The number of cells in the storage battery on a'motor vehicle is limited on account of cost,,weight,

and space required. The number of cells should be as low as possible in order to miniv mize'the initial cost, weight and space reh'ave-not more than six-cells, corresponding to approximately twelve volts. It IS a diflicult. problem to provide an acceptable dynamo-electric machine operating .from

such a low voltage which willdevelop a. sufficient torque to 'start theengine andbrmg it up to the desired speed. This difficulty is-increased where the same dynamo-elec- 'tric' machine is used as a generator for charging the battery, particularly as the charging operation should be started. at the lowest. possible generator-speed. It will be evi'de-nt'fron'i the foregoing-discussion that a=-dynatno-elcctric ma'chine -for an electric skirting, and light ng outfit should have. 50

\vheirope rating as a motor a'sflarge a-torque as'--possihle per pound of machine weight. That to say, the I quotient obtained .by-:dividin gjtl' qtourque of the machine expressed Fig.2 of the-drawings, while when operg tinfect pounds by the weight of the machine adapted for this use with which I am 'acquainted. While my invention inits complete form particularly relates to dynamo-' e lectrie machinesffor electric starting and l ghting outfits, fcert'ain features of the invention are generally applicable to" machines .for'other purposes. Thus,"certain featuresof my present invention maybe advantageou'sly utilized in the provision of a novel and improved 'dynamdeleetric machine. having compound excltation, while other featuresmay be employed 'to provide a; novel and improved direct current genorator of. approximately constant voltage over a relatively wide range speed. These and otherobjeets of my invention will be brought out'in the. course of thefollowing description.

The novel features which I believe to be patentably characteristic of my Invention are definitely pointed out intheclaims appended hereto. The" principle of myinvention and its applicationto d'irectfcur rent dynamo-electric machines will be' an ders'tood from the 'following "aesen uon taken. in' connection 'yvith the accompanying drawings, in which; i

Figures 1, 2 and 3 are diagrammaticviws illustrating machines" embodying the novel features-of my present invention Fig. 4

is an explanatory diagrammatievie'w'; and

. Figs. 5, 6, 7 8 and9' are explanatory fdiaams.

-- Fig. I of the drawings diagrammatically represents d km fl r cf achine embodying y p e n iinvention j i com plete form. This machfif p r u a-fly adap ped to operate on'the onefihandas' a 'ino- ,tomfor starting an internal combustion" engineand'on the other lipnd a generator ltage over a relaofpractically constailti zo .tiyely; wide range ofthei' niachineb normal operating speedsgwher'i operatic? ass 1- erator the maehii e'has :in genera I acterlsties of the machine frepresente'dflin theg'c aring as a motor the machine has the characteristics, and particularly the starting characteristics, of a compensated series motor of the type dia rammaticall represented in Fig. 4 of the drawings. M echanically, the machine of Fig. 1' is a combination of the machines of Figs. 2 and 4, and in the following exposition of my invention Lwill first discuss the machines of Figs. 2, 3 and 4.

Fi 4 diagrammaticall illustrates a twopole ynamo-electric mac ine having a commutated armature winding 12 and a series field winding 13, 14 distr buted over onehalf of the inner periphery of the field mag- 'net member. The relative directions of current flow in the conductors of these windin'gs are shown by means of the usual'convention in which crosses and circles applied to the conductors indicate, respectively, that the current is flowing away from or toward the observer. .The two halves .ot..the conductors of the armature winding between the commutator brushes 15 can currents flowing in opposite directions,- an thearmature' magnetization is thus alon the 'line aa. The field winding is distri uted over one-half of the inner periphery of the field magnet member, and in a' bi-polar mechmesuch as represented in Fig. 4, is distributed around the'two opposite quadrants of the armature winding and is designed to 'be connected in series therewith, so that it produces a magnetization at an angle of apnetization' produced'by the armature win ing. For the purposes of explanation'the field winding may be considered as comprising two equal component windings 13 and 14, as shown in Fig. .4; The ampere-turns 40 stantially equal to the armature ampereturns, so that the ampere-turns of each component winding are substantially equal to one-half the ampere-turns of the armature 4'5 winding, and the axis of magnetization of each component winding is displaced in space bysubstatiaIIy .45 electrical degrees from'the axis of magnetization of the armature winding. The component winding 14 combines with the two quadrants of the armature winding over the arcs AB and 0-D to form a uniformly distributed exciting winding having an axis of magnetization along the line e-e. That is to say, the winding 14 plus one-half of the armature .win'ding constitutes in effect an exciting windin distributed all around the peri liery of t e rotor of the machine. The ot er proximately electrical 'degrees to the mag-- of the entire field winding 13-114 are sub half of the armature winding over the aros- B-C and DA is adjacent the component winding 13, and since theradially adjacent conductors of these two windings carry currents flowing in opposite directions, the armature reaction dueto this half oi the armature winding is neutralized. Since the fieldwinding 13, 14 is connected in series with the armature winding and the strength of its magnetization is substantially equal to that of the armature winding, the armature reaction is in effect just neutralized at all loads, and the machine has the characteristics of a compensated series machine.

Fig. 3 of the drawings diagrammatically represents a bipolar machine of the type shown in Fi 4 having in addition a shunt exciting win gadapted to produce a magnetization substantially at 90 electrical degrees to the axis of magnetization of the armature winding. The field magnet structure or member 20 of the machine of Fig. 3 preferably has an oblong configuration for the purposes explained in my Letters Patent of t e United States No. 1,173,089, patented Feb. 22, 1916. The inner periphery of the field magnet member 20 is slotted in two opposite qilladrants', while the other two uadrants ave a' continuous peripheral surace. A winding 21 designed to be con-. nected in series with the armature winding is disposed in the slots of the field magnet 90 member and produces a ma etizationat an angle ,of substationally '45 ectrical degrees -to the axis of magnetization of the armaby the field winding 21 may be considered as composed of two equal components, one

of which coincides with and substantially neutralizes one-half of the armature reaction, while the other component combines with the other half of the armature reaction to form in efiect' a resultant flux at right ang'les, electrically, to'the armature reaction, thereby producing the exciting field of the machine. The winding 21 is connected in. se-' ries with the armature winding so as to neu-. tralize the-armature reaction at all loads.

The inner periphery of the field magnet member 20 is provided with wide slots or open spaces 25 in the zone of commutation. The provision of such wide slots increases the magnetic reluctance of he air gap in the commutatin zone and decreases -the magnetic flux in uencing the short-circuited armature conductors undergoing commutation, so that at most only a very weak magnetic field exists in the commutating zone, whereby a substantially neutral commutating zone is provided. The width of the slots .25 is such that the short-circuited armature coils undergoing commutation are located in this neutral commutating zone during the entire interval that they are short-circuited so that the electromotive force induced in such coils by their movement in this weak magnetic field is substantially negligible. The wide slots 25 are preferably closed with non-magnetic wedges 31, while the other slots in the field magnet iii ember are closed with magnetic wedges The use of non-magnetic wedges in the conimutating zone insures a clean-neutral commutating zone. In accordance with one feature of my present invention, the wide slots are used for the accommodation of a shunt field winding 26. Thus in Fig. of the drawings, each slot 25 is represented as occupied by one coil of the distributed. field winding 21 and two coils of the concentrated shunt. winding 26. The shunt Winding 26 is arranged to. produce an exciting magnetization at an angle of substantially 90 electrical degrees to the axis of magnetization of the armature winding, and by its use. a compound excitation of the machine may be obtained. Fig. 6 of the drawings diagrammatically represents the electrical connections and magnetic relations of. the three windings of the .machine illustrated in Fig-3. I

The machine diagrammatically represented in Fig. 2 of the drawings-hasafield winding consisting of two opposirsig shunt windings. The shunt winding '2 corresponds in everyrespect to the shunt winding. 26 of the machine (if-Fig. 3. The winding 27 is a bucking winding and itsmagnetization, while in line with that of the winding 26 is in opposition thereto. -It will be evident that' the excitation of the machine is thus the resultant of the magnctizations produced by the two windings 26' d 27". The machine is provided with an auxiliary pilot brush 28 hearing on the commutator The position of the pilot. brush 28 is determined by the pitch oi the coils of the bucking winding 27, as will be-m'ore fully explained hereinafter. The electrical connections of the windings of the machine of Fig. 2 are diagrammatically represented in Fig. 7. The arrows] indicate the relative directions of the currents flowing inthefield windings 26 and 27, and hence the relative directions of' their magnetizations The. bucking winding 27' is-show'n'in Fig. 7 as con nected between the pilothrush28 and the nearer main brush .24. i I 1'. v

T resultant ma gnetie fluxjproducedby. the two'field \-'indin gs' 23 --a-nd 27 diagrammatically represented in- Fig. The flat-topped wave 7' represents the flux .produced by the main shunt winding 26, while the horizontal lines 7) represent the depressions made in this fiux wave by the bucking flux produced by the winding 2T at difi'erent speeds" ot' the machine. The bucking winding 27- blows out'the fiuxproduced by the winding 26 over that' porti'on of the polar are bet een the'points a and d. The.

pilot brush 28 is so positioned that the armature coils between 1t and the main brush 2 .1. are not within the influence of that portion of the main shunt flux blown out by the bucking flux. Thus the pilot brush is shown in Fig. 5 as directly beneath the point 0. It will thus be seen that the bucking flux has no effect on the flux which is cut by the armature conductors'between the pilot brush 28 and the main brush 2+, between which two brushes the bucking winding 27' is conneeted; If we assume that the shunt winding 26 is excited from a source of direct current energy of substantially constantpotential. then its flux wave remains substantially the same for all speeds of the machine. The voltage which is induced in the armatureconductors between the pilot brush 28 and the main-brush 24. results from the movement of these armature conductors in that portion of the flux of the main shunt winding 26 which is not affected by the bucking winding and since this is a constant flux the voltage induced in thesearmature conductors varies directly with the speed of the machine. Therefore, as the speed of the machine increases, the magnitudev of the voltage impressed on'the bucking winding I 27 increases, and hence the bucking flux increases and-the depression in the fiux'.wavc f becomes deepen It will thus be evidentto those skilled in theartt'hat. the main shunt and bucking windings maybe so proportioned and designed that when the machine is operating-as agene'rator the-resultant exciting fielddecreases in strength as the speed of the machine increases; so that the voltage at the machines terminals is for inanypraiftical-purposes fairly constant over a relatively wide range of'speed. fl. 105

' I have found that thebest results are obtained witha machine of the type representedin Fig. 2, when thejportion of'the inner periphery of the field magnet member em-. braced or spanned by the bucking coils 27 110 is-operated ata low'fiux density; while the portions 30 of't-he field magnetstructure are" operated-at filiigh'fluxi density; In fact; I have rau'nd, that the" best results are obtained when thBIIIOItiOIlS, 30 are magnetically highly saturated If the machine isfpropoi tioned so as to obtainamagnetic saturation.

- in the different -p'ar'ts, as' just'described, it

will, when operating as a 'genera'toiflproduce approximately constant potential independent of the"speed.f i

The decrease in the resultant exciting field of the machineof Fig. 2 can be'made more pronounced for corresponding increases in speed'by connecting-the main shunt winding 125 26' between the'pilot brush 28 and the farthe-r main brush 34,-.'as ,rep1'e'sented in Fig. 9. Since the voltage between the brushes 24 and .28 increases with he speed of the machine, the voltage he ween the brushes 28,1 0

since it is connected in shunt to a whole or a part, as the case may be, of the armature winding, and it will of course be understood that where I hereinafter speak of the main exciting winding as connected in shunt relation to the armature winding I mean to cover both connections hereinbefore described. f

It will be evident from the foregoing explanation that the auxiliary brush 28 is ranged to produce a magnetization in line withbut opposed to-themagnetization produced by theexciting winding 26. The

electrical connections of the four windings the exciting field of the machine as the.

speed increases. Y

The machine represented in Fig. 1 combine's the desirable motor characteristics of a machine of the type represented in Fig. 4 with the constant voltage generator characteristics of a machine of the type represented so positioned on the commutator that the in F ig. 2. When operating as'a motor, the armature coils. between it and one of the main brushes are positioned inan approximately constant magnetic field over a rela-- tively wide range of the machines normal operating speeds. Theessential characteristic of the auxiliary brush is that the voltage between itzandone of the main brushes shall vary as a direct function of the speed of the machine'of Fig. 1 possesses decided series characteristics due to the efiect of the series field winding 21. This insures an excellent starting torque.- Furthermore, the machine is compensated so that no injurious sparking takes place during its operation as a motor I when the armature current is relatk cly large.

machine, and preferably directly as the motor, the starting current is very many speed, and while I have shown one arbe considered asthe constant'potential rangement .by which this can be accdmtimes, for example, in the neighborhood of twenty five times, the normal current when plished, other arrangements will suggest operating as a generator. Thus the effect of themselves to those skilled in the art. The bucking winding is thus. energized by a voltage preferably derived from the armature and varyingas a, direct funtiion of the speed of the machine and prefe, bly varying directly as the speed.

The machine represented in Fig. 1- may 11- erator represented in-Fig. 2 with'the a dition of a'distributed field-winding 21 arranged to produce a magnetization at an the predominating shunt components. The

the series'component of the resultant field series current is moreover substantiallyconstant during the operation of the machine angle of approximately 45 electric-'11 degrees as a generator. As a generator, the machine to the axis of the armature magnetization,

being thus in effect a. mechanical combination ofthe machines represented in Figs.

thus has in. effect a shunt excitation decreasing with the speed, so thatthe voltage at the terminals of the machine is for the purposes 2 and 4. The machine of Fig. 1 may also in handprac'tically constant.

be considered as the machine of Fig. 3'providedwith a bucking winding27 arranged and connected just as the bucking wind ng 27 ofthe machine of Fig. 2. The machine of Fig. 1 thus has a distributed field winding 21 connected in series relation with the armature winding 22-and arranged to pro clues. a magnetization at. anangle of approximately 45 electrical degrees to the axis of magnetization ofthe armature winding, anexciting winding 26 connected in shunt I have shown and particularly described .one embodiment of my invention for the purpose of generically explaining its prin- When the machine operates 'a a ciple and'its application, but numerous modirelation with the armature winding and ar: ranged to produce. a magnetization at'an angleof'approximately 9O electrical degrees to the axis of magnetization of the annature winding and a bucking winding 2? arfications of the details of construction and,

arrangement of this embodiment and-other applications. will. be apparentto those skilled in the art. I, therefore, wish to cover in the following claims all modifications within the spirit of the invention.

l-Vhat Iclaimas new and desire to secure by Letters Patentof the United States, is 1. A direct current dynamo-electric ma chine comprising an armature winding'provided with a commutator and eoiiperating main. brushes, a field magnet structure-having groups of distributed slots covering substantially one-half of its inner periphery, a series winding carried in the slots of said field magnet structure and arranged to pro duce a magnetization at an angle .of approximately 45 electrical degrees to the magnetization produced by said-armature win ing, a shunt exciting winding disposed on said field magnet structure and having coils spanning the larger part of the polar are on the inner periphery of said structure, a bucking winding having coils concentrically arranged within the coils of said exciting winding and spanning a smaller part of the polar are on the. inner periphery of said field magnet structure than the coils of said exciting winding, and an auxiliary brush located on said commutator so that the ar-i mature coils between it and a main brush are substantially outside the influencepf. the flux produced by said bucking winding, said bucking winding being connected between the auxiliary brush and the last mentioned main brush. i

2. A direct'current dynamo-electric machine comprisingan armature winding provided with a commutator and coiiperatmg main brushes, a field magnet structure having slots therein, a winding carried in the slots ofthe field magnet structure and arranged to produce a magnetization at an angle of approximately electrical degrees to the magnetization produced by bfl.l(1 armature winding, a shunt exciting winding disposed on said field magnet structure for producing a flux embracing the larger part of the polar are on the inner periphery of .said

structure, a' bucking-.winding disposed on said field magnet structure for producing a flux in opposition to theflux of said shunt. I

exciting winding but embracing asmaller part of the polar are, and'an auxiliary brush located on said commutator so that the armature coils between itand amain brush. are substantially outside the influence of the flux produced by said bucking winding, said bucking winding bein connected between the auxiliary brush an the last mentioned main brush.

3. A ,direct current dynamoelect i'ic machine comprising anal-mature winding provided with a commutator and cooperating "brushes, a winding arranged to produce ,a-

magnetization at an angle of approximately 45 electrical degrees to the magnetization produced by said armature winding, an ex-.

duced by, said armature winding, 2. bucking winding adapted toblow out a portion of thefiun produced by said excitin winding over a part only of the polar arc em raced by such flux, and means for exciting said bucking winding by an electromotive force derive main brushes, a field magnet structure having connected in shunt relation with thearmature winding and arranged on said'field magnet structure to produce a magnetiza- 7 tion at an angle of approximately 90 electrical degrees to the axis of magnetization of said armature windin a'buckingwin'ding arranged on said fiel magnet structure to produce a magnetization in line withlbut opposed to the magnetization produced by said' last mentioned shunt winding, and

meansfor energizing said-buckingwin'din from :1 source of electromotive force derive from said commutator and varying as adii'ect function of the speed of the machine.

5. A direct current dynamo-electric machine comprising an armature winding provided with-a commutator and cooperating main bIfllSllS,.aJ1 auxiliary brush bearing on said commutator, a field magnet structure carrying a. Winding connected in series re lation with the armature winding"ai 'id 'ar-' ranged to produce a magnetization-at an' angle of approximately 45 electrical degrees to the axis of .inagnetizatio'n ofsaid arinature winding, an exciting winding'connect ed in: shunt relation with the ar'iiialtur e winding and arranged on-s'aid field iiiii'gnet structure to produce a'inagneti zation-at. an angle of approximately 90 electrical"degrees to the axis of magnetization of said armature winding, :1. bucking winding arranged on said field magnet structure to produce. a.

magnetization in line with but opposedto the magnetization produced by s'aidflast mentioned shunt winding, and rna ns fw energizing said bucking winding from a vsource of electromotive force derived, from oneof said main brushes and said auxiliary brush located on said commutator so ithat the armature conductors betweenfltheaux brush are positioned in'an approximately constant magnetic held over Ea relatively wide range of the machines normal operating speeds.

- iliary brush and thelast mentionedfinain '6. A direct current dynamwel'ctriiiiina chine com rising an armature winding pro vided wit a commutator and cotiperating ing groups of distributed-slots covering sub? stantiallyone-half of its inner periphery, a

winding carried in said slots and arranged to produce a magnetization at an angle of approximately 45 electrical degrees to the axis of magnetization of said armature winding and adapted to be connected n series with the armature winding, an exciting winding connected in shunt relation with the armature winding and arranged on said field magnet structure to produce a magnetization at an angle of approximatel 9O electrical degrees to the axis of magnetization of said armature winding, a bucking winding arranged on said field magnet structure to produce a magnetization in line with but op osed to the magnetization produced by said last mentioned shunt winding, an auxiliary brush located on said commutator so-that the armature coils between it and a main brush are positioned in an pproximately constant magnetic field over a relatively wide range of the machines normal operatin speeds, and means for energizing said buc 'ng winding by .an electromotive force derived from said auxiliary brush and the last mentioned main brush.

7. A. direct current dynamo-electric machine comprising an armature winding pro-' vided with a commutator and cooperating main brushes, 9. field magnet structure carrying a-windmg connected in series relation .with the armature winding and arranged to produce a magnetization at an angle of approximately 45 electrical degrees to the axis of magnetization of said armature winding, an exciting winding connected in shunt relation to the armature winding and arranged on said field magnet structure to produce a magnetization at an angle of approximately 90 electrical degrees tothe axis of magnetization of said armature. windin a bucking winding arranged on "said field magnet structure to produce a magnetization in line with but opposed to the magnetization roduced by said last mentioned shunt win g, an auxiliary brush bearing on said commutator, and. means for energizby an electroing said bucking windingi t in ctio f rec n no motive force varying as a i the speed of the machine and. derived from .said auxiliary brush andone of said main brushes. I

- structure than the coils of the 'main exciting.

8. A chine comprising anarmature winding pro- 'vided with a commutator and a pair of 006perating main brushes, a field magnet structure carrying a-main exciting winding having coils spanning the larger part of the polararc on, the inner periphery of said fieldmagnet structure, a bucking winding having coils concentrically arranged within' the coils of said main exciting winding and spanning a smaller part of the olar are on the inner periphery of said eld magnet winding, and an auxiliary brush lqcated on said commutator so that the armature coils between it and an adjacent mainbrush are direct current dynamo-electric mawinding over a part only of the polar arc spanned by said main exciting winding, and means for excitin said bucking winding by an electromotive orce derived from armature coils located outside the influence of the flux produced-by said bucking winding.

10. A direct current dynamo-electric ma chine comprising an armature winding provided wit a commutator and cooperating main brushes, a shunt exciting winding arranged to span the lar er art of the polar arc of the machine, a inc g winding arranged to produce a flux in 0 position to the flux of said "shunt winding but spanning a smaller part of the polar arc, and an auxiliary brush locatedon said commutator so that the armature coils between it and an adjacent main brush are substantially outside of bucking winding, said buc g winding being connected betweenthe auxiliary "brush and said adjacent main brush.

11. A direct current dynamo electric machine comprising an armature winding provided with a commutator and a pair of cooperating main brushes, a field magnet structure carrying a main exciting winding havin coils spanning the larger. part of the 0 ar are on the inner periphery of said eld magnet structure, a hoe havingcoils concentricall -'arran the coils of said main exciting .wlndijiig and spanning a smaller part of the olar are on the inner periphery of said I eld magnet structure than the coils of the main exditisn winding, the magnetic'ma'terial of said field magnet structure being so proportioned that the portions of the pole face spanned by coils of both the main exciting winding and the bucking winding are operated at a low flux. density while the portions of the pole face spanned by only coils of the main exciting winding are. operated at a high flux density, and means for exciting said bucking winding by an electromotive force derived fromarmature coils located outside the influence of the flux winding.

' 12. A direct current dynamo=electric machine comprising an armature winding provided-with-a commutator and cooperating mair'iib'rushe a field magnet structure carrying an exciting winding connected in shunt a i n produced by said bucking relation with the armature winding, a buck i3!) wide range of the machines operating 10 speeds, an means for energizing said bucking winding b an electromotive force derived from sai auxiliary brush and the last mentioned main brush.

In witness whereof, I have hereunto set 15 my hand this 9th day of October, 1915.

SVEN, R. BERGMAN.

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